So I had a radiator that I just replaced less than 6 months ago blow on me again (I’ll attach pictures) so I got a new radiator, fan clutch and thermostat and couldn’t drive until I replaced at least the radiator and I did that just last weekend on the 2nd of December, 2023. The fan clutch and thermostat didn’t arrive until a few days later so I replaced the radiator and refilled the coolant, and I even replaced the ECT sensor at the back everything seemed to be going well engine wasn’t over heating or anything until today (12/07/23) on my way home from work and I made it home fine engine really started to heat up at an idle more than anything and fast too. I thought the problem was fixed until then. I’m probably gonna replace the fan clutch and thermostat either tonight or tomorrow (because they’re right next to each other and I have both parts sitting in the back of my 4Runner right now) I don’t know if those are the problems but I’m sure they are. If anyone else has any ideas on what could be the issue please respond to this thread. I’ll also update it once I replace the parts and see how the truck is running afterwards.
The new/ old (-6 months old) radiator when I took it out.


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Here’s the crack on that radiator


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What year & engine?

The bulged fins top & bottom + the crack look to me like the system was pressurized way past where it was supposed to be for some reason, then blew.

Have you replaced the radiator cap at all? iirc that's supposed to help prevent pressure buildup like that when working properly. I'd also be checking for other potential sources of extra pressure in the cooling system like a faulty HG.

2003, 1GR-FE, 290224 miles, I did replace the radiator cap. And I replaced the fan clutch and thermostat last night went to drive to work this morning and it still started to overheat, it may be due to me spilling some of the coolant and when I say some I mean a good amount when changing the thermostat. No check engine lights except when starting it does misfire I just replaced the spark plugs the other day and I’m wondering maybe I just need to top off the coolant now and burp the system and hopefully that’ll take care of that. As for the misfire I’m thinking that’s the ignition coils and won’t be too difficult to replace just one question anyone have any ideas or know what to do to get to the drivers side coils easier?


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But it is a good possibility that it is the HG I really hope not but it is on my to do list before the next move probably sooner rather than later.


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You've definitely got the right years, mileage, and motor for a HG issue. Especially if it's been overheated a few times.

It'd also explain the pressure buildup, so I'd definitely get a compression test done or check for some of the other common signs.

As for the coil packs, you should be able to unbolt the top & loosen the bottom of the metal bar running vertically near the rear 2 coils and then pull those pretty easily. Takes no time at all and as soon as it's loose it'll just swing out of your way.

You can also test coils by swapping them between cylinders to see if the issue moves around, but if it's the HG it's going to stay the same regardless of coil pack movement.

Ok well that will be fun with I’m sure. Another thing I didn’t mention earlier is that the heat was barely working.


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AM wondering if a bad cap could make the radiator not release built up pressure into the reservoir...and thus cause the radiator to crack

Head gasket is the first thing I would check. Leave the rad cap off and run the engine. Watch for exhaust bubbles coming out of the rad as the engine warms up. You can also buy a test kit to check for exhaust gasses in the antifreeze.